Arrangement of the oil pump in motor-compressor groups of refrigerating apparatus



Feb. 2, 1954 ARRANGEMENT OF THE OIL. PUMP IN MOTOR-COMPRESSOR GROUPS OF REFRIGERATING APPARATUS Filed Oct. 20. 1950 I. szANlszLo 2 668,007

7 INVENTOR. lstvon Szoniszlo Patented Feb. 2, 1 954 ARRANGEMENT OF THE OIL PUMP IN MOTOR-GOMPRESSOR GROUPS OF REFRIGERATING APPARATUS Istvan Szaniszlo, Caronno Pertusella (Varese), Italy, assignor to Siemens Societa per Azioni, Milan, Italy, a corporation of Italy Application October 20, 1950, Serial No. 191,096

Claims priority, application Italy July 10, 1950 '5 Claims. (Cl. 230-206) In refrigerators with motor-compressor sets, the lubricating oil is generally in direct contact with the refrigerant which has the property of dissolving in the oil. The amount of refrigerant dissolved in the oil is the greater, the higher the oil temperature and the vapor pressure of the refrigerant.

During idle periods of the motor-compressor set, the state of saturation is soon reached, a relative maximum of refrigerant then being absorbed by the oil.

This phenomenon is the cause-of the following deficiency:

Whenever the set starts functioning after a rest period of not too short a duration, the reduction in vapor pressure of the refrigerant due to the starting of the compressor, momentarily disturbs the equilibrium between the dispersed phase (refrigerant) and the dispersing phase (oil). This results in a sudden and abundant formation of bubbles of refrigerating medium within the oil which, tending to escape from the oil, transform the latter into a foaming mass.

Moreover, normal oil pumps are not capable of inducting foamin oil. Hence, in the absence of special devices, the lubrication would be deficient a certain period of time, that is until the oil has freed itself of a good part of the refrigerating medium dissolved therein. The object of the present invention is to avoid this deficiency even under the most unfavorable working conditions.

According to the invention, the motor-compressor set of a refrigerator has its housing provided with a dividing wall which extends, within the oil quantity contained in the bottom portion of the housing, in substantially parallel relation to the free surface of the oil. The submerged wall divides the oil into two layers. The intake opening of the oil pump is disposed at the center of the dividing wall and at such a depth as to induct oil only from the upper layer.

According to a particularly advantageous embodiment, the dividing wall is formed by the body of the oil pump itself, and the intake opening of the pump is located at the center of the pump body and is directed towards the free surface of the oil.

The intended improvement is the more marked, the larger the pump body extends in the horizontal direction. It is therefore preferable to use a centrifugal pump with a scroll-type casing and an impeller of a vertical axis, the central suction opening being located in the center of the housing that encloses the set so that the oil enters the pump at a point at which the saturation of the oil is well known'to be a minimum for any conditions of operation.

The invention is illustrated, by way of example, in the accompanying diagrammatic drawing which shows a motor-compressor set with a centrifugal oil pump in section along a plane through the axis of rotation of the motor.

The motor-compressor set, enclosed by a housing I, has a compressor 2' operated by an electric motor 3. The compressor is shown to be of the reciprocating type and has its piston linked to a crank l l on the shaft l2 of the motor. Shaft l2 carries the rotor iii of the motor. The aeriform refrigerant is sucked in through a tube '9, then compressed in the compressor '2, and delivered to the successive parts of the refrigerating apparatus through a tube H1. The lubrication of the set is effected by a centrifugal pump having a scroll-type casing 5 and an impeller 6. The pump axis is vertical. The impeller 6 may be driven by the shaft [2 of the motor 3, as is the case in the illustrated example, or it may be driven separately. The oil circulated by the pump is distributed in the known manner to the various points to be lubricated by means of an oil line Id. The pump is completely immersed in the oil 8 and divides the oil quantity into two layers: an upper thin layer and a lower layer. The oil inlet opening of the pump is located at the center of the pump and at the center of the housing I. Suction takes place from top to bottom.

When the pump starts to operate, the oil converges from the upper thin layer towards the central inlet opening '5 and must pass in a thin layer over a path at least equal to the radius of the pump. During this passage the oil has all the time required to free itself from a large quantity of the refrigerating medium dissolved therein. This action is greatly aided by the thinness of the layer. Moreover, the thin layer of oil travelling towards the suction inlet of the pump, cannot absorb new amounts of refrigerating medium because throughout its travel this oil is completely separated from the remainder of the oil.

In any conditions of operation the pump will thus be fed with oil less saturated with refrigeratin medium. This does not prevent the initially inducted oil from being possibly still partly frothy when the pump is started. This, however, does not reduce the effectiveness of the lubrication since, while passing through the impeller, the oil gradually increases its pressure so that any vapor bubbles that may still be formed do not have such a size as to interrupt the flow of oil.

WhatIclaim is:

1. In a refrigerating motor-compressor set having a sealed enclosure filled with refrigerant when in operation and having a bottom portion containing an approximately constant quantity of lubricating oil forming a free level surface, a dividing wall structure extending substantially parallel to said level surface and in proximity thereto and being submerged in said oil quantity so as to divide part of said quantity into two layers above and below said structure, and lubricating pump means having an inlet opening disposed at the center of said wall structure and within the upper one of said layers to induct oil only from said upper layer.

2. In a refrigerating motor-compressor set having a sealed enclosure filled with refrigerant when in operation and having a bottom portion containing a quantity of lubricating oil forming a free level surface of approximately constant height, a Wall structure submerged in said oil quantity in proximity to said surface and extending over a central portion of the cross sectional area of said housing so as to divide said quantity in said central portion into two horizontal layers merging with each other beyond said central portion, the upper one of said layers being shallow in comparison with the horizontal dimension of said central portion, and lubricating pump means havin an oil inlet opening at the bottom of said upper layer and substantially on the vertical center axis of said wall structure to induct oil only from said upper layer, said inlet opening being directed toward said level surface.

3. In a refrigerating motor-compressor set having a sealed enclosure filled with refrigerant when in operation and having a bottom portion containing a quantity of lubricating oil forming a free level surface, a lubricating pump having a casing, said casing having a substantially horizontal wall portion disposed in said oil quantity near the level of said quantity and being surrounded by said quantity so as to divide from said quantity a shallow upper layer, said pump having an oil inlet opening disposed in said upper oil layer substantially at the center of said wall so as to induct oil only from said upper layer.

4. In a refrigerating motor-compressor set having a sealed enclosure filled with refrigerant when in operation and having a bottom portion containing a quantity of lubricating oil forming a free level surface, a dividing wall structure extending near and substantially parallel to said level surface and being submerged in said oil quantity and surrounded thereby so as to divide said quantity into a lower layer and a shallow upper layer, and lubricating pump means having an oil inlet opening located substantially on the vertical center axis of said housing and at the bottom of said upper layer to induct oil only from said upper layer.

5. In a refrigerating motor-compressor set having a sealed enclosure filled with refrigerant when in operation and having a bottom portion containing a quantity of lubricating oil forming a free level surface, a centrifugal lubricating pump having a vertical axis and having a pump casing horizontally disposed in said quantity and surrounded thereby so as to divide said quantity into a shallow upper layer and a lower layer, said pump casing having a smaller horizontal dimension than said housing and said two layers merging with each other at the periphery of said casing, said casing having an oil inlet opening concentric to said axis and disposed at the bottom of said upper layer to induct oil only from said upper layer.

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References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,274,943 Touborg Mar. 3, 1942 2,463,251 Curtis Mar. 1, 1949 2,469,086 Shepherd May 3, 1949 

